Problem: In math class, the girl to boy ratio is $5$ to $3$. If there are a total of $24$ students, how many girls are there?
Solution: A ratio of $5$ girls to $3$ boys means that a set of $8$ students will have $5$ girls and $3$ boys. A class of $24$ students has $3$ sets of $8$ students. Because we know that there are $5$ girls in each set of $8$ students, the class must have $3$ groups of $5$ girls each. There is a total of $15$ girls in math class.